Contactless push button switch

ABSTRACT

A contactless push button switch comprising a magnetic circuit including a magnet, stationary yokes, a movable yoke and a fieldsensitive element (such as reluctance effect element, hole effect element, SMD, etc.), said magnetic circuit being disposed between a button cover and a base of the switch. By depressing the button cover the movable yoke is caused to undergo a physical change, thereby extremely reducing the density of the magnetic flux penetrating the field-sensitive element to cause a change of the terminal voltage or electro-motive force across the fieldsensitive element so as to bring about the switching action of the switch.

FIF85112 XR 516818 1025 A United States Patent [151 3,680,025

Kobayashi 1 1 July 25, 1972 [s41 CONTACTLESS PUSH BUTTON OTHERPUBLICATIONS SWITCH IBM Technical Disclosure Bulletin, Vol 6, No. 11,April,

[72] Inventor: Tsunekazu Kobayashi, Kawasaki, Japan 1964 Funk et al.,variable Mode Pushbutton Switch Assignee: onkyo p y Unified Tokyo,Primary Examiner-D. F. Duggan Japan Arramey-Chittick, Pfund, Birch,Samuels & Gauthier [22] Filed: Sept. 18, 1970 [21] Appl.No.: 73,391

[57] ABSTRACT A contactless push button switch comprising a magneticcircuit including a magnet, stationary yokes, a movable yoke and ForeignAllllncamm Priority Data :1 field-sensitive element (such as reluctanceeffect element, Sept. 19, 1970 Japan ..45/88864 hole effect element 1Said magnetic cimuil being Sept 9, 1970 Japan 45 13 3 5 disposed betweena button cover and a base of the switch. By

depressing the button cover the movable yoke is caused to un- [52] U.S.C1 ..338/32, 335/1, 310/10 de go a physical change. thereby extremelyreducing the den- [51] Int. Cl ..I-l01c 7/16 sity of the, magnetic fluxpenetrating the field-sensitive ele- [58] Field of Search ..310/DlG. 10,15; 335/1, 2; ment to cause achange of the terminal voltage orelectro-mo- 338/32 R, 32 H tive force across the field-sensitive elementso as to bring about the switching action of the switch. [56] ReferencesCited UNITED STATES PATENTS 8 CM 8 Dr I n ms, aw n res 3,537,046 10/1970l-lubrich et al ..338/32 R x g PAIENTEDJum-s m2 SHEEI 1 (IF 2 FIG. 3

F IG.

FIG. 2

I NVENTOR TSUNEKAZUA Ko'BAYAsm BY l 1-? CONTACTLESS PUSH BUTTON SWITCHBACKGROUND OF THE INVENTION This invention relates to contactless pushbutton switches and, more particularly, to contactless push buttonswitches utilizing the effects of a change of magnetic field intensityon a field-sensitive element such as relactance efiect element, holeelement, SMD, etc.

Heretofore, table electronic computors, push button telephone sets andvarious other apparatus have used lead switches having mechanicalcontacts such as spring contacts.

These mechanical contact switches require relatively large I space forinstallation on the, installation panel. Also, they are likely to giverise to misfunctioning of the system using them due to chattering causedwhen their contacts are made and broken.

Meanwhile, owing to the recent advance in the IC technique variousminiatuarized electronic circuits are readily produced, giving rise tothe demand for small-size and highly reliable switches.

SUMMARY OF THE INVENTION The principal object of the invention,accordingly, is to pro vide a contactless switch, which uses afield-sensitive element and a magnet to utilize the phenomenon that theelectromotive force or terminal voltage across the field-sensitiveelement changes with change in the intensity of magnetic fieldthereacross, and which can provide an excellent switching characteristicsuitable for use in combination with transistors and other activecircuit elements.

Another object of the invention is to provide a contactless push buttonswitch using a field-sensitive element, which is of a constructionrequiring a relatively small extent of displacement of the switch buttonto produce the switching action though the top area of the button isslightly large.

A further object of the invention is to provide a contactless pushbutton switch using a field-sensitive element, in which the top area ofthe switch button is reduced.

A still further object of the invention is to provide a contactless pushbutton switch using a field-sensitive element, which is free from aspring providing a restoring force against the depression of the switchbutton.

A yet further object of the invention is to provide a contactless pushbutton switch using a field-sensitive element, which has two or moremagnets to permit the selection of the intensity of themagnetic fieldacross the field-sensitive element.

The contactless push button switch according to the invention comprisesa magnetic circuit disposed between a switch button-cover and a switchbase and including one or more magnets, stationary yokes, a movable yokeand a field-sensitive element (such as reluctance effect element, holeelement, SMD, etc.), these components being arranged in such a mannerthat by depressing the switch button-cover at least part of the movableyoke is rotated about the top of a stationary yoke, thereby extremelyreducing the density of the mag netic flux across the field-sensitiveelement to cause a change of the terminal voltage or electro-motiveforce across the field-sensitive element so as to bring about theswitching action of the switch. Thus, the service life of the switchaccording to the invention can be extended almost infinitely owing tothe freedom from the switch contacts unlike the conventional leadswitches. Also, extreme reliability is ensured owing to the freedom fromthe chattering of the switch contacts. Further, the reduction of theswitch size may be readily attained, as it is possible to accommodateall the essential component parts within the switch button-cover.

These and other objects, features and advantages of the invention willbecome more apparent from the description of the illustrated preferredembodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a plan view showing anembodiment of the contactless push button switch according to theinvention. FIG. 2 is a section taken along line IIII' in FIG. 1.

FIG. 3 is a section taken along line III-III in FIG. I.

FIG. 4 is a plan view showing another embodiment of the contactless pushbutton switch according to the invention.

FIG. Sis a section taken along line V-V' in FIG. 4.

FIG. 6 is a section taken along line VI-VI' in FIG. 4.

FIG. 7 is a sectional view showing a further embodiment of theinvention.

FIG. 8 is a sectional view showing a still further embodiment of theinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIGS. 1 to 3,a preferredembodiment of the contactless push button switch according tothe invention is shown having a casing comprising a switch button-coverI having a substantially square top surface and a switch base 2 having abase area smaller than the area of the bottomopening of the switchbutton-cover l. The switch button-cover l is provided with two parallellegs 4 extending from the inside 3 of its top wall. The legs 4 extendthrough respective openings 5 formed in the switch base 4. Wound oneachleg 4 is a spring 6 disposed between the inside face of the top wall ofthe switch button-cover l and the top face of the switch base 2, sothatwhen the switch button-cover I is depressed the springs 6 urge it to itsoriginal position relative to the switch base 2 as shown in FIG 2. Eachleg 4 is provided on the side of the switch base 2 opposite the spring 6with a cotter pin 21 serving as a stopper to determine the inoperativeposition of the switch button-cover I. The cotter pin 21 also serves toprevent the vibration of the switch button-cover 1 when the button-coveris depressed and ensure reliable downward displace-ment of the switchbutton-cover. The switch base 2 is secured to a panel 20 by means of acentral bolt 17 and a nut 18. The bolt 17 is embedded in the switch base2. An elongate magnet 7 lies on top of the switch base 2. It is incontact with and longitudinally held between fixed yokes 8 and 9. As isseen from FIGS. 2 and 3, the fixed yoke 8 extends upright from theswitch base 2 beyond the magnet 7,.and it is provided on the inner sideof its portion extending beyond the magnet 7 with a field-sensitiveelement I0, which is in contact with both the yoke 8 and the magnet 7.The leads of the field-sensitive element 10 are taken out at leadterminals 19. The other fixed yoke 9, whose height is less than that ofthe fixed yoke ,8, has its top in contact with a movable yoke II. Themovable yoke 11 has a straight portion terminating .in front of thefield-sensitive element 10 as indicated at 12 and the remaining portionextending toward the bottom opening of the switch buttoncover I andterminating in the vicinity of the corner wall 14 thereof as indicatedat 13. The corner of the switch buttoncover 1 corresponding to the end13 of the movable yoke 11 has a thick wall portion 15 terminating in aninclined shoulder 16 terminating in the portion 14.

By the term field-sensitive element" appearing throughout thespecification is meant the well-known element such as reluctance effectelement and hole element which has certain properties undergoing achange-in the presence of a magnetic field. It is used as an element toprovide switching function by utilizing the change of the electricresistance ad as a control element to generate a control voltagecontrolling a switching element (such as a transistor and thyristor).

The fixed yokes 8 and 9 and the movable yoke 11 are made of a magneticmaterial. Thus, when the switch button-cover I is held in itsinoperative position shown in FIG. 2 by the urging force of the springs6, the end of the movable yoke 11 supported on top of the fixed yoke 9is attracted to the magnet 7. In this state, the yokes 8, 9 and 11 andthe magnet 7 form a closed magnetic loop, so that the field-sensitiveelement 10 in front of the end 12 of the movable yoke 11 is placed inthe magnetic field present in the magnetic circuit. Thus, thefieldsensitive element 10 offers a high resistance if it is a reluctanceeffect element. If it is a hole element, a hole voltage appears at thehole terminal.

In the operation of the embodiment described above, when the switchbutton-cover I is not depressed but is held in itsinoperative positionwith respect to the switch base 2 by the urging force of the springs 6as shown in FIGS. 2 and 3, the fieldsensitive element 10 offers a highresistance or provides a high bole voltage. In this state, when theswitch button-cover I is depressed against the spring force of thespring 6, the inclined shoulder 16 of the switch button-cover 1 pushesdown the end 13 of the movable yoke 11 to cause the rotation of themovable yoke 11 about the top of the fixed yoke 9 in the clockwisedirection in FIG. 2. As a result, the end 12 of the movable yoke 11 isdisplaced away from both the field-sensitive element I and the fixedyoke 8. This means that the field-sensitive element is displaced out ofthe magnetic circuit. In other words, the intensity of the magneticfield across the field-sensitive element 10 is reduced to a negligiblevalue. Thus, if the field-sensitive element 10 is a reluctance effectelement its resistance is reduced, and if it is a hole element its holevoltage is extremely reduced. With this change a switching signal may ofcourse be produced. When the pressure on the depressed switchbutton-cover 1 is released, the switch button-cover is forced back toits original inoperative position as shown in FIGS. 2 and 3 by therestoring force of the spring 6.

In the embodiment described above, the switch buttoncover 1 is providedwith two legs 4 extending from the inside face 3 of its top wall andpenetrating through the switch base 2. These legs are employed tostabilize the frictional movement of the switch button-cover 1 towardthe switch base 2. The two legs are thus by no means limitative, but anysuitable number of legs may be employed. Also, the shoulder constructionconstituted by the inclined shoulder 16 between the wall portions 14 and15 of the switch button-cover 1 is not limitative, and any alternativemeans may be used so long as such means is brought into emgagement withand pushes down the end 13 of the movable yoke 11; for example, aprojection may replace the inclined shoulder 16.

As is described, in the preceding embodiment the substantial portion ofthe movable yoke extends along the longitudinal direction of theelongate magnet supported on the switch base, so that the straightportion of the movable yoke from its pivotal point to its end in frontof the field-sensitive element, that is, the portion of the movable yokeconstituting the magnetic path, may be made sufficiently long. In otherwords, the preceding embodiment has the advantage that a relativelysmall extent of displacement of the switch button-cover is required tobreak the magnetic circuit of the movable yoke though the area of thetop of the switch, that is, thetop of the switch button-cover, isslightly large. Thus, the contactless push button switch in thepreceding embodiment may be effectively used for apparatus, in which thearea of the switch installation is sufficiently available but thedistance of the displacement of the'switch button-cover toward theswitch base is not sufficiently available.

FIGS. 4 to 6 show another embodiment of the contactless push buttonswitch according to the invention. The illustrated switch has a casingcomprising a switch button-cover 31 having a substantially square topsurface. and a switch base 32. The switch base 32 is secured to a panel49 by means of a threaded projection 47 extending from the switch base32 and a nut 48 fitted on the threaded projection 47. The switchbutton-cover 31 is provided with a leg 34 extending from the inside face33 of its top wall. The switch button-cover l is also formed with aguide bore 35. The switch base 32 is formed with an opening 36, throughwhich the leg 34 extends, and provided with an upright upper projection37 extending into the bore 35. On the leg 34 is mounted a spring 38disposed between the top wall 33 of the switch button-cover 31 and theswitch base 32, so that when the switch button-cover 31 is depressed thespring 38 urges it toward its original position relative to the switchbase 32 as shown in FIG. 5. The leg 34 is provided on the side of theswitch base 32 opposite the spring 38 with a cotter pin 50 serving as astopper to determine the inoperative position of the switch button-cover31. The cotter pin 50 also serves to prevent the vibration of the switchbutton-cover 31 when the button-cover is depressed and ensure reliableaction of the switch. In this embodiment, an elongate rectangular magnet39 lies on a first fixed yoke 40 supported on the switch base 32. On topof the magnet 39 lies a second fixed yoke 41. The second fixed yoke 41is formed at one end thereof with a projection 42 pivotally supporting amovable yoke 43. The movable yoke 43 has a straight portion terminatingin front of a field-sensitive element 45 placed on the first fixed yoke40, as indicated at 44. It is bent at its point in contact with the topof the projection 42, and its upper portion then upwardly inclined andterminates in an end portion 46 substantially parallel to the insideface 33 of the top wall of the switch button-cover 31. The first andsecond fixed yokes 40 and 41 and the movable yoke 43 are made of amagnetic material. Thus, when the switch button-cover 31 is held in itsinoperative position shown in FIG. 5 by the urging force of the spring38, the lower end 44 of the movable yoke 43 supported on the projection42 of the second fixed yoke 41 is attracted to the magnet 39. In thisstate, the yokes 40, 41 and 43 and the magnet 39 form a closed magneticloop, so that the field-sensitive element 45 in front of the lower end44 of the movable yoke 43 is placed in the magnetic field present in themagnetic circuit. Thus, similar to the previous embodiment, if thefieldsensitive element 45 is a reactance effect element, it offers ahigh resistance, while if it is a hole element, a hole voltage appearsat the hole terminal.

In the operation of this embodiment, when the switch button-cover 31 isnot depressed, it is held in its inoperative position with respect tothe switch base 32 by the urging force of the spring 38 as shown inFIGS. 5 and 6. In this state, similar to the previous embodiment, thefield-sensitive element 45 offers a high resistance or provides a highhole voltage. When the switch button-cover 31 in this state is depressedagainst the spring force of the spring 38, the inside face 33 of its topwall pushes down the upper end portion 46 of the movable yoke 43 tocause the rotation of the movable yoke 41 about the top of theprojection 42 of the second fixed yoke 41 in the counterclockwisedirection. As a result, the lower end 44 of the movable yoke 43 isrevolved in the counterclockwise direction away from the field-sensitiveelement 45 and the first fixed yoke 40. This means that thefield-sensitive element 45 is displaced out of the magnetic circuit. Inother words, the intensity of the magnetic field across thefield-sensitive element 45 is reduced to a negligible value. Thus, ifthe field-sensitive element 45 is a reluctance effect element itsresistance is reduced, and if it is a hole element its hole voltage isextremely reduced. With this change a switching signal may of course beproduced. When the pressure on the depressed switch buttoncover 31 isreleased, the switch button-cover if forced back to its originalinoperative position as shown in FIGS. 2 and 3 by the restoring force ofthe spring 38.

In this embodiment, the substantial portion of the movable yoke extendsalong the longitudinal direction of the elongate magnet erected on theswitch base, so that the area of the top surface of the switchbutton-cover may be reduced as compared to the previous embodiment.Thus, the contactless push button switch in the preceding embodiment maybe effectively used when installing many switches in a panel of aconstant area.

FIG. 7 shown a further embodiment of the invention. Its casing comprisesa switch button-cover 51 having a substantially square top surface and aswitch base 52 having a base area smaller than the area of the bottomopening of the switch button-cover 51. The switch base 51 is secured toa panel 60 by means of a central bolt 58 and a nut 59. An elongatemagnet 53 lies on top of the switch base 52. It is in contact with andlongitudinally held between fixed yokes 54 and 55. The fixed yoke 54extends upright from the switch base 52 beyond the magnet 53, and it isprovided on the inner side of its portion extending beyond the magnet 53with a field-sensitive element 57, which is in contact with both theyoke 54 and magnet 53. The other fixed yoke 55, whose height is lessthan that of the fixed yoke 54, has top in contact with a movable yoke56.

The movable yoke 56 has a straight portion terminating in front of thefield-sensitive element 57 as indicated at 56. The remaining portion ofthe movable yoke 56 extends downwardly from the pivotally supportedspot, is folded back upwardly and terminates in an upper end portion 56"substantially parallel to and in contact with the inside face of the topwall of the switch button-cover 51.

The operation of this embodiment is essentially the same as theoperation of the preceding embodiments shown in FIGS. 1 to 4 and inFIGS. 4 to 6, so the detailed description of the operation will not begiven here.

In this embodiment, the coil spring or springs as in the precedingembodiments of FIGS. 1 to 3 and of FIGS. 4 to 6 is dispensed with, thusreducing the number of component parts.

FIG. 8 shows a modification of the embodiment of FIG. 7. In the Figure,the same parts or similar parts having the same function as those shownin FIG. 7 are designated by identical reference numerals. Thisembodiment differs from the embodiment of FIG. 7 in that in thisembodiment another magnet 53' is bonded to the fixed yoke 54 on the sideopposite the magnet 53. With this construction by appropriatelyselecting the size, configuration and material of the second magnet 53',the intensity of the magnetic field in the magnetic circuit may beselectively varied to, in turn, vary the amount of pressure which mustbe applied to depress the switch button-cover 51.

What is claimed is:

l. A contactless push button switch comprising a boxshaped switchbutton-cover having an open bottom and at least one leg extendingdownwardly-from the inside of the top wall of said switch button-cover,a switch base located below and adapted to fit within said switchbutton-cover, said switch base being formed with at least one opening,each of said legs of said switch button-cover being guided through oneof said openings, a spring mounted on each of said legs, each of saidsprings providing restoring force against the displacement of saidswitch button-cover toward said switch base, an elongated magnet lyingon top of said switch base and within said switch button-cover, saidmagnet extending horizontally and being provided at opposite ends withfixed yokes, the second one of which extends above said magnets, afield-sensitive element fixed on the inner side of a portion of thesecond one of said fixed yokes, said field-sensitive element being incontact with both said second fixed yoke and said magnet, and a movableyoke pivotally supported on top of the first one of said fixed yokes,said movable yoke having a portion on the side of the pivotal supportpoint nearer to said field-sensitive element which constitutes amagnetic circuit together with said field-sensitive element, said switchbutton-cover having an inwardly projected portion adaptedto push downthe portion of said movable yoke extending on the other side of saidpivotal support point to pivot said movable yoke and break said magneticcircuit when said switch button-cover is depressed against the forces ofsaid springs.

2. The contactless push button switch according to claim I, wherein eachof said legs is provided on the side of said switch base opposite saidswitch button-cover with a projection serving as a stopper and saidprojections also serve to prevent the vibration of said switchbutton-cover when said switch buttoncover is depressed and ensurereliable downward displacement of said switch button-cover.

3. The contactless push button switch according to claim 2 wherein eachof said projections is a cotter pin.

4. A contactless push button switch comprising a switch button-coverhaving a leg extending from the inside face of the top wall of saidswitch button-cover, said switch button-cover being formed with a guidebore, a switch base formed with an opening and provided with an uprightprojection, said leg of said switch button-cover being guided throughsaid opening and said upright projection extending into said bore ofsaid switch button-cover, a spring mounted on said leg of said switchbutton-cover, said spring providing restoring force against thedisplacement of said switch button-cover toward said switch base, anelongated magnet erected over the top of said switch base, said magnetbeing provided at opposite ends with fixed yokes, a field-sensitiveelement in contact with both the upper face of the first one of saidfixed yokes and a side face of said magnet, and a movable yoke pivotallysupported on top of a projection of the second one of said fixed yokes,said movable yoke havinga portion on the side of the pivotal supportpoint nearer to said field-sensitive element which constitutes amagnetic circuit together with'said field-sensitive element, and whereindepression of said switch button-cover against the force of said springcauses the inside face of the top wall of said switch button-cover topush down the end of a portion of said movable yoke extending on theother side of said pivotal support point to break said magnetic circuit,and wherein said leg is provided on the side of said switch baseopposite said switch button-cover with a projection serving as a stopperand said projection also serves to prevent the vibration of said switchbutton-cover when said switch buttoncover is depressed and to ensurereliable downward displacement of said switch button-cover. I

5. The contactless push button switch accordingly to claim 4, whereinsaid projection is a cotter pin.

6. A contactless push button switch comprising a switch button-cover, aswitch base, an elongated magnet lying on top of said switch base, saidmagnet being provided at opposite ends with .fixed yokes, the second oneof which extends beyond the top face of said magnet, a field-sensitiveelement in contact with both the inner side of a portion of the secondone of said fixed yokes extending beyond said magnet and the top face ofsaid magnet, and a movable yoke pivotally supported on top of the firstone of said fixed yokes, said movable yoke having a portion on the sideof said pivotal support point nearer to said field-sensitive elementwhich constitutes a magnetic circuit together with said field-sensitiveelement and a portion on the other side of said pivotal supportpointwhich extends downwardly from said pivotal support point, is then foldedback upwardly and terminates in an end portion in contact with the topwall of said switch button-cover, whereby depression of said switchbutton-cover causes rotation of said movable yoke to break said magneticcircuit, and further comprising a second magnet whose magnetic fieldinteracts with said magnetic circuit so that the intensity of themagnetic field in said magnetic circuit is adjustably selecting the sizeand material of said second magnet.

7. A contactless push button switch comprising a boxshaped switchbutton-cover having an open bottom and a leg extending downwardly fromthe inside face of the top wall of said switch button-cover, said switchbutton-cover being formed with a downwardly extending guide bore, aswitch base formed with an opening and provided with an uprightprojection, said leg of said switch button-cover being guided throughsaid opening and said upright projection extending into said bore ofsaid switch button-cover, a spring mounted on said leg of said switchbutton-cover, said spring providing restoring force against thedisplacement of said switch buttoncover toward said switch base,anelongated magnet located within said switch button-cover and erectedover the top of said switch base, said magnet being provided at oppositeends with fixed yokes, a field-sensitive element in contact with boththe upper face of the first one of said fixed yokes and a side face ofsaid magnet, and a movable yoke pivotally supported on top of aprojection of the second one of said fixed yokes, said movable yokehaving a portion on the side of the pivotal support point nearer to saidfield-sensitive element which constitutes a magnetic circuit togetherwith said field-sensitive element, and wherein depression of said switchbutton-cover against the force of said spring causes the inside face ofthe top wall of said switch button-cover to push down the end of aportion of said movable yoke extending on the other side of said pivotalsupport point to break said magnetic circuit.

8. A contactless push button switch comprising a boxshaped switchbutton-cover having an open bottom, a switch base located below andadapted to fit within said switch button-cover, an elongated magnetlying within said switch butsaid field-sensitive element and a portionon the other side of said pivotal support point which extends downwardlyfrom said pivotal support point. is folded back upwardly and ter minatesin an end portion in contact with the top wall of said switchbutton-cover, whereby depression of said switch button-cover causes therotation of said movable yoke to break' said magnetic circuit.

*0 l l l l

1. A contactless push button switch comprising a box-shaped switchbutton-cover having an open bottom and at least one leg extendingdownwardly from the inside of the top wall of saiD switch button-cover,a switch base located below and adapted to fit within said switchbutton-cover, said switch base being formed with at least one opening,each of said legs of said switch button-cover being guided through oneof said openings, a spring mounted on each of said legs, each of saidsprings providing restoring force against the displacement of saidswitch button-cover toward said switch base, an elongated magnet lyingon top of said switch base and within said switch button-cover, saidmagnet extending horizontally and being provided at opposite ends withfixed yokes, the second one of which extends above said magnets, afield-sensitive element fixed on the inner side of a portion of thesecond one of said fixed yokes, said fieldsensitive element being incontact with both said second fixed yoke and said magnet, and a movableyoke pivotally supported on top of the first one of said fixed yokes,said movable yoke having a portion on the side of the pivotal supportpoint nearer to said field-sensitive element which constitutes amagnetic circuit together with said field-sensitive element, said switchbutton-cover having an inwardly projected portion adapted to push downthe portion of said movable yoke extending on the other side of saidpivotal support point to pivot said movable yoke and break said magneticcircuit when said switch button-cover is depressed against the forces ofsaid springs.
 2. The contactless push button switch according to claim1, wherein each of said legs is provided on the side of said switch baseopposite said switch button-cover with a projection serving as a stopperand said projections also serve to prevent the vibration of said switchbutton-cover when said switch button-cover is depressed and ensurereliable downward displacement of said switch button-cover.
 3. Thecontactless push button switch according to claim 2 wherein each of saidprojections is a cotter pin.
 4. A contactless push button switchcomprising a switch button-cover having a leg extending from the insideface of the top wall of said switch button-cover, said switchbutton-cover being formed with a guide bore, a switch base formed withan opening and provided with an upright projection, said leg of saidswitch button-cover being guided through said opening and said uprightprojection extending into said bore of said switch button-cover, aspring mounted on said leg of said switch button-cover, said springproviding restoring force against the displacement of said switchbutton-cover toward said switch base, an elongated magnet erected overthe top of said switch base, said magnet being provided at opposite endswith fixed yokes, a field-sensitive element in contact with both theupper face of the first one of said fixed yokes and a side face of saidmagnet, and a movable yoke pivotally supported on top of a projection ofthe second one of said fixed yokes, said movable yoke having a portionon the side of the pivotal support point nearer to said field-sensitiveelement which constitutes a magnetic circuit together with saidfield-sensitive element, and wherein depression of said switchbutton-cover against the force of said spring causes the inside face ofthe top wall of said switch button-cover to push down the end of aportion of said movable yoke extending on the other side of said pivotalsupport point to break said magnetic circuit, and wherein said leg isprovided on the side of said switch base opposite said switchbutton-cover with a projection serving as a stopper and said projectionalso serves to prevent the vibration of said switch button-cover whensaid switch button-cover is depressed and to ensure reliable downwarddisplacement of said switch button-cover.
 5. The contactless push buttonswitch accordingly to claim 4, wherein said projection is a cotter pin.6. A contactless push button switch comprising a switch button-cover, aswitch base, an elongated magnet lying on top of said switch base, saidmagnet being provided at opposite Ends with fixed yokes, the second oneof which extends beyond the top face of said magnet, a field-sensitiveelement in contact with both the inner side of a portion of the secondone of said fixed yokes extending beyond said magnet and the top face ofsaid magnet, and a movable yoke pivotally supported on top of the firstone of said fixed yokes, said movable yoke having a portion on the sideof said pivotal support point nearer to said field-sensitive elementwhich constitutes a magnetic circuit together with said field-sensitiveelement and a portion on the other side of said pivotal support pointwhich extends downwardly from said pivotal support point, is then foldedback upwardly and terminates in an end portion in contact with the topwall of said switch button-cover, whereby depression of said switchbutton-cover causes rotation of said movable yoke to break said magneticcircuit, and further comprising a second magnet whose magnetic fieldinteracts with said magnetic circuit so that the intensity of themagnetic field in said magnetic circuit is adjustably selecting the sizeand material of said second magnet.
 7. A contactless push button switchcomprising a box-shaped switch button-cover having an open bottom and aleg extending downwardly from the inside face of the top wall of saidswitch button-cover, said switch button-cover being formed with adownwardly extending guide bore, a switch base formed with an openingand provided with an upright projection, said leg of said switchbutton-cover being guided through said opening and said uprightprojection extending into said bore of said switch button-cover, aspring mounted on said leg of said switch button-cover, said springproviding restoring force against the displacement of said switchbutton-cover toward said switch base, an elongated magnet located withinsaid switch button-cover and erected over the top of said switch base,said magnet being provided at opposite ends with fixed yokes, afield-sensitive element in contact with both the upper face of the firstone of said fixed yokes and a side face of said magnet, and a movableyoke pivotally supported on top of a projection of the second one ofsaid fixed yokes, said movable yoke having a portion on the side of thepivotal support point nearer to said field-sensitive element whichconstitutes a magnetic circuit together with said field-sensitiveelement, and wherein depression of said switch button-cover against theforce of said spring causes the inside face of the top wall of saidswitch button-cover to push down the end of a portion of said movableyoke extending on the other side of said pivotal support point to breaksaid magnetic circuit.
 8. A contactless push button switch comprising abox-shaped switch button-cover having an open bottom, a switch baselocated below and adapted to fit within said switch button-cover, anelongated magnet lying within said switch button-cover and on top ofsaid switch base, said magnet being provided at opposite ends with fixedyokes, the second one of which extends above said magnet, afield-sensitive element in contact with both the inner side of a portionof the second one of said fixed yokes and the top face of said magnet,and a movable yoke pivotally supported on top of the first one of saidfixed yokes, said movable yoke having a portion on the side of saidpivotal support point nearer to said field-sensitive element whichconstitutes a magnetic circuit together with said field-sensitiveelement and a portion on the other side of said pivotal support pointwhich extends downwardly from said pivotal support point, is folded backupwardly and terminates in an end portion in contact with the top wallof said switch button-cover, whereby depression of said switchbutton-cover causes the rotation of said movable yoke to break saidmagnetic circuit.